Tension control apparatus for conduit laying and retrieval



I Umted States Patent 111135 [72] Inventor Peter S. Rlegel [56] References Cited Columbus, Ohio UNITED STATES PATENTS 1 pp 3,123,270 3/1964 Olson 226/162X 1 Flled Nov-7,1968 3,143,309 8/1964 Clarke 226/195X [45] Patented Nov. 17, 1970 [73] Assignee Columbia Gas System Service Corporation Schachel' New York, New y Attorney- Penme, Edmonds, Morton, Taylor and Adams a corporation of Delaware M ABSTRACT: This disclosure relates to an apparatus for controlling the tension of a conduit during its laying or retrieval between a marine platform and an underwater surface. [54] E J; $:X: FOR CONDUIT Gripping units having shoes for frictionally gripping the con- 5 CM 8 3 Dnwh H s duit are held within a range of positions relative to the platm g B form using a cable systemand these units are positioned in [52] US. Cl 226/39, tandem so that while one unit grips the conduit the other unit 226/195 may move along the conduit to take a grip on the conduit at a [51] Int. Cl B65]: 23/18 different position relative to the marine platform. Shoes are [50] Field of Search 226/39, moved against the conduit by resilient members and withdrawn by hydraulic units.

Patented Nov. 17, 1970 3,540,642

Sheet 1 of 2 INVENTOR PETER S. RIEGEL ATTORNEYS A Patented Nov. 17, 1970 3,540,642

Sheet 2 of 2 mvemoR PETER s. RIEGEL ATTORNEYS BACKGROUND OF THE INVENTION In the continuous laying of conduits it is necessary that the conduit be guided and controlled as it is discharged from or retrieved to the platform or deck of the laying vessel. It is also required that the conduit be permitted to move relative to the platform or barge to accommodate for movement of the conduit due to wave action, vessel speed change, change in depth of water and other variations which affect the rate of movement of the conduit from the platform.

The maintenance of proper tension in the conduit during the laying operation permits the conduit to be positioned in the water during its descent and ascent in the proper configuration tominimize strain in the conduit. Since the strain developed in conduits during their laying is often critical to the design of the conduit, savings in weight and cost can be achieved by controlling the strain induced during the movement of the conduit.

While a number of apparatus have been proposed for accomplishing proper tension of conduits during handling the disclosed apparatus provides an effective and reliable manner for successfully accomplishing a high degree of tension control under the varied marine conditions including variations in vessel movement, water action and water depth.

SUMMARY OF THE INVENTION The present invention provides an apparatus for the continuous controlling of the tension in a conduit as it is moved between a movable platform and an underwater surface which apparatus includes a plurality of units for gripping the conduit which units are tandemly arranged and are coordinated to be operated together to control the tension of the conduit.

Broadly, the present invention comprises a plurality of conduit gripping units positioned in tandem to grip a substantially straight section of the conduit, frictional engaging means mounted on each unit including a plurality of shoes urged by resilient members into frictional engagement with the conduit and including means for urging the shoes away from the conduit to release their engagement, interconnecting means for interconnecting the units, variable tensioning means for varying the amount and direction of tension in the interconnecting means, movable tension sensing means for sensing the tension in the interconnecting means and control means for selectively causing the gripping units to grip and release the conduit and for controlling in response to the tension sensing means the amount and direction of the tensions created by the tension means.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is an elevational view ofa gripping unit;

FIG. 2 is a sectional line taken along line 2-2 of FIG. I; and FIG. 3 is a plan view of the apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring particularly to F IGS. l and 2, it is seen that pipe 1 is supported on flanged roller 2 having axle 3 mounted for rotation in bearing stand 4 on deck or platform 6. The number of rollers required to support the pipe or conduit will vary depending on the length and stiffness of the pipe.

Frictional gripping unit A includes frame 7, shoes 8 pivotably mounted on arms 9 and pipe guide wheels 11 journaled in bearings 5 secured to frame 7. Wheels 11 roll on the surface of the pipe to center the pipe in the gripping unit. Shoes 8 are curved to correspond with the curvature of the pipe. Springs 12 move the shoes against the surface of the pipe where the angle of arms 9 and the tendency of pipe to move to the right (FIG. 1) causes the shoes and pipe to be urged against one another with sufficient force to prevent relative movement between the shoes and the pipe.

Turning now to FIG. 3, gripping unit B, which has the same; construction as unit A, is secured to another cable 19. Both'lv cables have their ends secured to cable terminals 21 on reciprocating piston rod 23 which is positioned for movement in hydraulic cylinder 24. A piston mounted on piston rod 23 within cylinder 24 is urged to the right, as viewed in FIG. 3, when hydraulic pressure is applied to cylinder 24 from reversible variable delivery pump 22 through line 25 and the piston rod is urged to move to the left when hydraulic pressure is applied through line 26 to the other side of the piston.

A control unit 27 includes means for controlling pump 22 to vary its discharge pressure into line 25 or line 26. The control unit receives a signal from accumulator unit 43 through pressure line 49 which signal energizes suitable means to vary the discharge pressure of pump 22 and the controlunit is further actuated through associated limit switches 29 and 33 to in line 49 increases, control unit 27 controls pump 22 to decrease the pump discharge pressure.

When one of the cable terminal units 21 including its depending arm 31 moves a sufficient distance to the right or left due to a corresponding movement of the gripping units it strikes one of the pivotable switch arms 32 of switches 29 or 33 to cause hydraulic fluid to be pumped to the side of the piston in cylinder 24 which will cause the piston, the piston rod 23 and the cable terminal units 21 to be urged to move in the other direction.

Guide pulleys 28 mounted on shafts 29 together with movable tension sensing unit 30 guide and tension cables 18and 19. The cables 18 and 19, their supporting pulleys 28, the cable terminals 21 and the piston rod 23 provide an interconnecting arrangement between the gripping units to enable the units to move relative to deck 6 when the pull of the pipe is greater or smaller than the tensioning forces urging the engaged gripping unit.

Return cables 18a and 19a are also connected between the terminals 2] and the gripping units A and B. These cable sections are tensioned only as required to move a gripping unit which is not engaged with the pipe. The inactive unit is moved in a direction opposite to the movement of the engaged gripping unit to be readied for its turn as an active gripping unit.

More than two gripping units maybe used provided they are arranged to operate in two groups, one group actively engaging the pipe while the other group is disengaged.

Tension sensor unit 30 has rotatable pulleys 34 and 36 to engage cable 18 and 19, respectively, both pulleys being rotatably positioned on movable longitudinal frame 37 tandemly-connected to piston rod 38. Rod 38 has a piston mounted on it and positioned within hydraulic cylinder 39 where the resulting hydraulic pressure from rod 38 being urged to the left (FIG. 3) varies with the tension in cables 18 and 19. The hydraulic fluid in cylinder 39 communicates through conduit 41 with accumulator unit 43 which includes a the compression of the gas in compartment 48. Unit 30,

cylinder 39 and accumulator unit 43 function together to sense the tension in the cable system and to transmit a pressure signal to control unit 27 indicating the amount of tension in the system.

Unit 30 pulls with a force equal to twice the sum of the tension forces in cables 18 and 19 so that as one cable is relaxed and the other tensioned the total tensioning force transmitted to the pipe remains constant. Cables 18 and 19 pull on unit 30 with forces equal to twice their tension to create a balance when the system is static.

The pressures in hydraulic lines 17 are preferably controlled through suitable means in control unit 27 and are supplied by a hydraulic pump source, such as pump 22. Control unit 27 may also include a coordinating device for coordinating the gripping action of the gripping units and the direction of movement of piston rod 23 to tension selectively unit A or unit B.

It is contemplated that fuel-carrying pipes, electrical transmission lines, communication cables and other conduits whether flexible or not may be handled by the present apparatus.

Before the operation of the illustrated apparatus is commenced, the pipe is positioned within the gripping units A and B by activating hydraulic cylinders 14 to retract the shoes and permit the pipe to be passed through the units using any suitable marine pipe handling gear. When during the operation of the apparatus to discharge or retrieve the pipe control of the tension in the pipe is desired, the hydraulic cylinders of one unit, such as unit A, are deactivated permitting springs 12 to move the shoes in contact with the pipe while the shoes of unit B are held away from the pipe. The angle of arms 9 and the tendency of the pipe to move to the right (H68. 1 and 3) causes the shoes to firmly grip the pipe. The force of the tension in the pipe when balanced by the tension in cable 18 holds the unit A in substantially a fixed position relative to the platform.

When the pipe moves to the right due to increased weight of the payed out pipe or other cause, tension in cable 18 is increased as gripping unit A moves with the pipe. Piston 38 is able to move to the left (FIG. 3) through the resilient effect of increasing pressure in cylinder 39 and accumulator unit 43. The increase pressure in compartment 48 of the accumulator is sensed by control unit 27 to decrease the discharge pressure of pump 22. The decrease in pump discharge pressure allows piston 23 to move to the left which in turn allows unit A to move to the right while maintaining substantially the same amount of tension in pipe 1.

As unit A moves a sufficient distance to the right (FIG. 3) to pull cable terminal arm 31 to the left to activate arm 32 of switch 28, control unit 27 reverses the pump to cause it to discharge into line 26 to urge piston rod 23 to the left. Control unit also deenergizes cylinders 14 of unit B to permit the shoes of that unit to engage the pipe. As rod 23 moves to the left, cable 19 is tensioned to cause unit B to grip the pipe and cable 18 is slackened but the total force urging pipe 1 to the left remains constant. When-the tension in the pipe is desired to be increased or decreased the amount of pressure in cylinder 24 is varied through control of pump 22.

The purpose of permitting unit A to release the pipe and unit B to engage the pipe is to control the tension in the pipe through use ofa gripping system of practical size. When substantial increases in tension of the pipe occur unit A need travel only a limited distance in an effort to maintain a constant tension until the second unit takes over. If an increase in tension continues unit A will again take over when unit B has moved to the right to cause terminal 21 to activate switch 29. At this point inactive unit A will have moved to the left and will be ready to grip the pipe and operate within an effective range of operable movement until unit B is again reactivated. As a unit is moved in the same direction as the pipe tends to move, which is the direction shown by the arrow of FIGS. 1 and 3, shoes 8 will slide over the pipe surface. Cylinder units 14 may not be required where these frictional forces are not substantial.

lclaim:

1. In an apparatus for controlling the tension in a conduit moving from a platform:

a. two conduit gripping units positioned in tandem arrangement adjacent the conduit, each unit independently capable of being activated to grip the conduit and deactivated to release the conduit;

b. interconnecting means for connecting the units to one another and to the platform;

c. tension means for tensioning the interconnecting means to urge with variable forces the active engaging unit in the direction opposite to conduit movement;

d. resilient movable tension sensing means for resiliently resisting movement of the units engaging the conduit and for sensing tension in the interconnecting means;

e. actuating means for defining the range of movement of the gripping units and for activating the tensioning means to urge selectively one of the gripping units in a direction opposite to conduit movement;

f. control means for selectively engaging one of the units with the conduit while disengaging the other gripping unit and for controlling the tension means; and

g. coordinating means for coordinating the control means and the actuating means so that when one gripping unit moves to one end of its range the other gripping unit is caused to grip the conduit and the tension means is activated to tension the then active gripping unit.

2. In an apparatus for tensioning a conduit during its laying and retrieval between a platform and a marine bottom:

a. support means mounted on the platform for supporting substantially a straight length of conduit;

b. a plurality of mo able gripping frames positioned adjacent the length of pipe;

c. a frictionally-engaging shoe mounted on each frame for movement against and away from the pipe to frictionally engage and release the pipe;

. power means for urging the gripping shoes away from the pipe to release the pipe;

e. control means controlling the power means to move the gripping shoes such that only one frame remains actively engaging the pipe;

f. support means for permitting the gripping frames to reciprocate in a path parallel to the pipe;

g. variable tension means connected to the support means for moving the active gripping frame: and

h. limit means responsive to the support means for operably applying the tension means to move one gripping frame and then another.

3. The apparatus of claim 2 in which the support means is an arrangement of cables and pulleys and in which the tension means is a hydraulic piston and cylinder unit.

4 An apparatus for varying the fric tional forces applied to a conduit as the conduit passes over a marine platform comprisa. two movable frictional gripping units, each unit in turn comprising: i. aframe; ii. a plurality of shoes; mounted for movement on the frame; and iii. means for urging the shoes against the conduit;

b. two elongated flexible elements each having one end connected to one of the gripping units and the other end connected to a reciprocating piston rod for urging either unit in a direction opposite to the direction of conduit travel;

c. a plurality of flanged rollers to support the flexible elements;

:1. a tension sensing unit positioned between the ends of the flexible elements to sense tension in each flexible element said tension unit in turn comprising:

i. a movable frame; ii. a pair of rotatable elements on the frame for engaging each of the flexible elements; iii. a piston and cylinder unit-connected to the frame for varying pressure in the cylinder as the frame moves; and

urge one active gripping unit and the other active gripping unit in directions opposite to conduit movement.

5. The apparatus of claim 4 in which the flexible elements are cables and the power means for moving the piston rod is a hydraulic cylinder and pump means for varying the pressure in the cylinder. 

